Press for the production of hot-pressed sheets



June 30, 1970 E. S IEMPELKAMP 3,517,610

PRESS FOR THE PRODUCTION OF HOT-PRESSED SI'IEIEJ'I S I 2 Sheets-Sheet 1Filed Sept. 19, 1967 Eugen Svempelkamp INVENTOR.

B Y R055 Attorney June 30, 1970 E. SIEMPELKAMP PRESS FOR THE PRODUCTIONOF HOT-PRESSED SHEETS 2 Sheets-Sheet Filed Sept. 19, 1967 EugenSiempelkamp INVENTOR.

Attorney United States Patent 3,517,610 PRESS FOR THE PRODUCTION OFHOT-PRESSED SHEETS Eugen Siempelkamp, Hohenzollernstr. 69, Krefeld,Rhineland, Germany Filed Sept. 19, 1967, Ser. No. 668,805 Claimspriority, application Germany, Jan. 12, 1967, S 107,833; Jan. 19, 1967,S 107,899 Int. Cl. B30b 7/02, 15/34; B02c 11/08 US. Cl. 100198 5 ClaimsABSTRACT OF THE DISCLOSURE A multiplaten press for the production ofhot-pressed board from comminuted material, such as wood or othercellulosic fibers with or without addition of a binder, and method ofoperating such press, wherein the raw layer of comminuted material isfed between the heated platens of the press with interposition of asheet-metal heat-conductive liner in surface contact with the respectiveplatens in the closed condition of the press, the liners being mountedto define a narrow gap breaking heat conductivity between themselves andthe platens when the press is opened. An array of nozzles direct coolinggas (e.g. air) against the liners to cool them without cooling theplatens which are continuously heated.

My present invention relates to a platen process for the production ofcoherent sheet material and, more particularly, for the hot pressing ofcellulosic fibers, chips, particles or the like in the presence of anatural or artificial thermally activated binder to form coherent sheetsfrom layers of non-coherent or loosely coherent materials.

The production of pressed board has played an increasingly significantrole in the' structural-material field and, indeed, pressed boards ofnumerous types are cur rently available, the types depending in part.upon the comminuted material used therein, the densities to which theboards are pressed and the types of binder. For example, fiberboard,chipboard, beaverboard and other coherent plates or sheets can be formedfrom cellulosic fibers or comminuted wood using the lignin inherentlyfound therein as the binder or with the addition thereto of binders suchas phenol-formaldehyde resins.

In most cases an apparatus for the production of such binders comprisesa dispenser for depositing a layer of loosely coherent or noncoherentcomminuted material upon a receiving surface which may be passed into aprepress or which may deposit the layer upon a charging plate, movablemetallic van or the like for introduction into a platen press. In my US.Pats. Nos. 3,050,200 and 3,077,271, I describe various apparatus of thisgeneral type for the production of pressed board in which a stack ofcharging levels adjacent one side of a multiplaten press feeds the rawlayers of comminuted material onto respective tiers of a multiplaten ora multistage press, while means is provided on the other side of thispress for leading the pressed and coherent sheets therefrom. In my US.Pat. No. 3,050,777, for example, I describe and claim a multilevel pressof this general character while my Pat. No. 3,241,189 describes andclaims the structure and technique involved in the heating of theplatens.

It will be recognized that, where multiplaten presses are concerned,there are two basic methods of operating the installation. In onesystem, the layers charged into the press are supported upon so-calledcharging trays or plates which may be advanced into the press anddeposited upon the lower platen of each tier. Heat transfer to therespective layer takes place through the rigid charging plate which,when the press is reopened, carries the "ice now rigid and densifiedsheet from the press. This system has advantages in that there is nodistortion of the layer when it is advanced in the nonpressed conditioninto the press but involves difficulties with respect to recirculatingthe charging trays to the dispensing station and with respect to thecooling of the plates as is required for their further handling. In amodification of the system, the noncoherent layer of comminuted materialis drawn into the press on a so-called band support which consists ofmore or less flexible sheet material characterized by ease of cooling.This band may be associated with the platen in such manner as toeliminate the need for circulation. However, complex drive arrangementsare required for the band tablets and trays. In the system set forth inthe first-mentioned group of patents, an alternative method of chargingand discharging multiplaten pressures wherein the noncoherent or looselycoherent layers of comminuted material are deposited upon the platens ofthe press by respective conveyor belts designed to let on the layers ata rate such that there is no substantial distortion thereon. A similarmethod of transporting such layers and charging the press is describedin US. Pat. No. 3,332,819. When these methods are employed, the layer isdeposited upon the lower platen of each tier of a multiplaten press, thepress is closed to compact all of the layer simultaneously and, uponopening of the press, the sheets of coherent material are pushed fromtheir layer platens onto a discharging station whose tiers correspond innumber to those of the press. From the discharging station, the coherentsheet may be led to an annealing or tempering kiln or the like. Sucharrangements also involve difiiculties since the press platens cannotalways be continuously heated and direct contact of the noncoherentlayers with platens at a temperature of compression causes destructionof the layer, gas evolution or the like. Cooling of the platens beforethe layers are deposited thereon is uneconomical with respect to theheat balance and, because of the mass of the platens, requiresconsiderable time, thereby limiting the rate of production of thesheets.

It is, therefore, the principal object of the present invention toprovide an improved method of operating a platen-press installation forthe production of hot-pressed sheets which permit an increased rate ofproduction, reduces the possibility of thermal distortion of thepressable layers and requires low capital expense.

Another object of this invention is to provide an apparatus for theproduction of hot-pressed board whereby the disadvantages of earliersystems may be obviated.

These objects and others which will become apparent hereinafter areattainable in a system wherein a multiplaten press having a pair ofvertically spaced horizontal platens at each press stage and with atleast the lower platens thereof heated, is provided along the lowerpress platens with a thermally conductive (e.g. sheet metal) coolingsheet or liner adapted to form a slight gap between its major surfaceregions and the corresponding regions of the heated press platen whenthe press is open; in the closed condition of the press, this liner,which is interposed between the layer of comminuted material and theheated surface of the platen, is in heat-conductive surface contact withthe platen to transfer heat to the layer during the compression stroke.Advantageously, means is provided externally of the press or within thepress platen for directing a stream of cooling gas (e.g. air) along theliner surface.

According to a further feature of this invention, the sheet-metal lineris affixed to the respective press platen along opposite edges thereofby a resiliently deflectable support extending above the heated surfaceof the platen and about which the liner is turned and anchored. Thus theliner is resiliently supported on its respective platen and can bebiased by normal press closure and the elevated press pressure intosurface contact therewith; upon opening of the press and removal of thecoherent sheet, the liner springs into its predetermined spacing fromthe heated surface so that the sheet-metal liner may be cooled by thegas jet, advantageously passing in part through the gap and directedalong the surface of the liner remote from the gap without materiallycooling the continuously heated platen. In this manner, it is possibleto cool the sheet to a temperature of 250 to 200 C. or less. The nozzlesfor directing the cooling air along the liners, which may beadvantageously disposed along both sides of each layer and along theupper and lower platens defined in each press stage, can be oriented andarranged in Various ways. For example, the nozzles can be disposed alongthe periphery of the plates orformed in the platens directly oppositethe liners. In the latter case, the press surface of the platen isformed with the nozzles which are connected to a dispensing network ofcooling channels built into the pressed platen. When the nozzles areoriented in this manner, the liner is supported upon a cushion ofcooling air in addition to or aside from the resilient support meansdescribed earlier. The channels and nozzles must be so oriented that theliner is practically level and is yet subjected to uniform cooling bythe gas and I have found that the cooling gas flow should be, to fulfillthese conditions, stronger at the edges of the liners or platens than inthe central zones thereof.

According to the method aspect of this invention, the gap between theliner and the pressed platen should be of the order of 0.8 mm. while thetemperature of the liner is preferably reduced to about 200 to 150 C.Furthermore, the thickness of the liner and its total mass should besuch that it can be brought to this temperature by contacting thecooling stream in a period of seconds or less. Advantageously, the lineris composed of a material of high thermal conductivity (e.g. stainlesssteel).

It has been found that this arrangement has the significant advantagethat materials of high conductivity, when serving as a liner, not onlypermit rapid cooling of the surface to contact the incoming layer ofcomminuted material but also provide rapid heating of this layer uponpress closure. In addition, I have found that advantage is gained by thefact that thermal transfer through the liner takes place only when thepress cycle has indeed begun to be effective uponthe particular layerand not prior thereto. In effect, the liner produces a delay in theheating of the layer until compression has commenced, which delayincreases the quality of the coherent sheet produced by activating thebinder after initial compression. A substantial saving in thermal energyis obtained concurrently with an increase in the cycle rate of the presswhich has been found to be particularly effective even with so-calleddry-pressed board.

The above and other objects, features and advantages of this inventionwill become more readily apparent from the following description,reference being made to the accompanying drawing in which:

FIG. 1 is a diagrammatic elevational view of a press embodying thisinvention;

FIG. 2 is a detailed view showing the arrangements of the nozzles ofthis press; and

FIG. 3 illustrates another nozzle arrangement but showing the means forsupporting the liners on the platens of FIGS. 1 and 2.

As diagrammatically illustrated in FIG. 1, an apparatus for themanufacture of chipboard sheets, fiberboard sheets, and the likeincludes multiplaten press 10 with, in the example shown, a number ofpressing plates or platens 12 vertically spaced from each other, toform, between each pair of press platens 12, pressing chambers orpassageways 14 in tiers (see US. Pats. Nos. 3,209,405 and 3,050,777).The device also includes a press-charging station generally indicated at16, with stacked conveyor belts or the like 18, and also a dischargeapparatus, generally indicated at 22, for discharging or emptying thepressing chambers 14 of the finish-pressed panels or sheets 20, whichhave been formed from the raw or partly fabricated non-coherent layers24 (see US. Pats. No. 3,050,200, No. 3,077,241, and No. 3,288,057).

The conveyor belts pass under a conventional spreading or distributinghopper station not shown, from which a quantity of fibrous or comminutedchip material or the like is deposited on them, which is to form the rawor partially fabricated sheets 24. The fibers may be dampened, suppliedwith a binder or otherwise treated either in the hopper or spreader orthereafter as needed, and may be subjected to an initial rough pressingoperation by a rough-forming press which shapes them into the raw orrough layers 24. They are carried by band conveyors, charging plates orthe like and ultimately arrive at the respective delivery apparatusstation 16, in tiers one above the other.

Referring again to FIGS. 1 and 2, it is seen that there are providedcooling liners or sheets 26 of sheet metal, which extend across and overthose surfaces of the pressing plates 12, which form the interiorsurfaces of the pressing chambers 14. Thus, when the rough-formed layers24 are moved into their respective tier of pressing chambers 14, fromstation 16, with the press in opened position as shown, they are not indirect contact with the pressure plates 12, but always have liners 26inbetween their upper and lowersurfaces and the respective plates.

Means are provided (see FIG. 3) whereby, when the press is in openedposition as shown, the cooling liners are spaced from their relatedpressure plates by the small spacing indicated by a, forming a narrowgap or passageway between the lining and pressure plate. This feature isindicated on a larger scale in FIG. 2. Of course, when the press isactuated, so that the pressing plates move downwardly, apart from thelowermost plate, then the cooling liners 26 are pressed against theirrelated pressing plates 12, with the raw sheets inbetween relatedcooling liners and out of direct contact with the pressing platesthemselves. It is to be noted that the pressure plates of the press areprovided with heating ducts (see FIG. 3 or my patents cited earlier) formaintaining them at a predetermined temperature suitable for theparticular material and operation being worked upon.

Cooling nozzles 28 are provided around the cooling liners 26, theembodiment disclosed providing the nozzles 28 about the side edges ofthe cooling liners and also about their end edges, preferably as needed.Additional or supplementary nozzles 28 may also be provided asnecessary. From each of the cooling nozzles 28 there is discharged acooling gas, for example, air, at the time when the press 10 is in openposition and the pressing plates 12 at their maximum interspaciug.

FIG. 2 shows arrows 30 which illustrate the path of the cooling gasentering each tier of the press, so that the gas covers each entirecooling liner 26 and thus cools it off, e.g. to a temperature from 200C. to C.; that is to say, that the cooling action is to be carried outto a point at which the comminuted layers are no longer adherent to oraffected by the liner surfaces.

The latter result can be reached in a few seconds, since the coolingliners 26 themselves are'made of thin metal of good heat conductionqualities. According to a preferred form of the invention, each pressingchamber is lined with upper and lower cooling liners whereby, upon theclosing of the main press 10, the raw-material layers 24 in the pressingchambers are subjected simultaneously to pressure on both their upperand'lower surfaces from the liners. The interspacing a between eachcooling liner and its related pressing plate upon opening of the press,may, for example, be about 0.8- mm., according to a preferred example.

In the operation of the aforementioned apparatus, th rough-materiallayer 24 may be fed into respective tiers of pressing chambers 14 withthe aid of the belt conveyors 18, by causing the conveyors to moverapidly in a direction toward the main press 10, and then to suddenlystop and reverse them or by holding fast their drive belts 32. Thus, byinertia, each of the rough-material sheets 24v is thrown forwardly intoits respective tier of pressing chambers 14. The pressing plates 12 arecontinuously heated, but cooling liners or trays 26 have experienced theabove-mentioned cooling action by air blast and are spaced by thedistance a from their related pressing plates 12. When the main press isagain closed, the cooling liners press against the pressure plates 12,and the heat conduction resumes, so that the cooling liners 26 arequickly heated whereby further the closing of the main press results ineffective pressing action from both the upper and lower surfaces of thepressing plates, as mentioned. When the press opens again, the blastsfrom the air-cooling nozzles not only exert cooling action, but alsoforce the liners 26 away from their related pressing plates, and alsofrom the finished pressed sheets 20, which are removed to the right asseen in FIG. 1 to suitable trays for storage or the like.

FIG. 3 shows the means for actuating the cooling liners and allowingmovement to normal open-press spaced positions from their positions whenthe press is closed.

As illustrated in FIG. 3, there are pressure plates 12a and 12b whichrepresent those at 12 of FIGS. 1 and 2. Upon the closure of the mainpress 10, as explained, any raw-material sheets in the pressing chambers14, between adjacent overlying pressure plates, will be pressed intofinished form.

At least the lower platen 12b, according to the embodiment shown, isprovided with a cooling liner or sheet 40, generally corresponding toliners 26 of FIG. 1. The cooling liner 40 is normally maintained whenthe press is open, in its solid-line position, spaced to the extent ofinterspacing 42 to form a fluid passageway 44 therebetween. The supportis such that the cooling sheets 40 are subjected to tension along theirentire length. When the pressing operation takes place, the arrow 46shows that each of the cooling sheets 40 is pressed against its relatedpressure plate such as 12b. It is also seen that each surface of thepressure plates 12a, 12b is provided with cooling gas nozzles 48 leadingfrom gas ducts 50, for conducting from a source, a cooling pressurizedgas such as air to the nozzles. When the press is opened, then thecooling gas from nozzles 48 serves to press the cooling liners 40 awayfrom the pressure plates such as 12b, and exerts a cooling effect, asshown in solid lines, from their broken-line position 40a.

In order to place the cooling liners under tension as mentioned,supports include at the opposite edges of each platen, a spring plate 54which is wider than the thickness of the pressure plate as shown in fulllines, and is slidably mounted on the bolt 56 which in turn is threadedinto the respective edge of the pressure plate. The spring plate 54 isspaced from the edge of the pressure plate by the block 58, as shown,and each of the edges of each cooling liner sheet 40 is bent over andsecured to the edges of the spring plate 54 by means of screws 60 andwashers 62. Ducts 64 serve to heat the platen.

It is thus seen that when the press is open, the spring plate 54 isrelatively flat and maintains the cooling liners 40 in tension and flatand spaced from the related pressure plate. When the press is closed,the cooling liners 40 are pressed to positions 40a against the pressureplate, and the spring plate 54 assumes the convex position shown inbroken lines. Upon opening of the press, the spring plate immediatelyreturns to flat position, and places the liner sheets 40 under tensionand spaced from the pressure plates. The blocks 58 are narrower than thepressure plates, and are secured thereto by the same bolts 56.

The invention described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodifications being considered within the spirit and scope of theinvention.

Iclaim: 1. In an installation for producing pressed board wherein alayer of comminuted material is hot-pressed to form a coherent sheet andincluding a platen press having at least one pressing stage and at leasttwo platens receiving said layer between them, means for heating atleast one of said platens, means for relatively shifting said platenstoward and away from one another to compress said layer and releasesame, the improvement which comprises:

at least one sheet-metal liner interposed between said layer and saidone of said platens for heat-conductive surface contact therewith uponmovement of said platens toward one another for transferring heat tosaid layer; means operatively connected with said liner and effectiveupon movement of said platens away from one another to space said linerfrom said one of said platens and break heat-conductive contacttherebetween at least along the major portions of the surfaces of saidliner and said one of said platens; and

means for subjecting said liner to a stream of a cooling fluid includingnozzle means disposed along an edge of said liner and trained towardsaid liner for directing said stream of cooling fluid at least in partbetween said liner and said one platen.

2. The improvement defined in claim 1 wherein each of said platens isprovided with a respective sheet-metal liner interposed between it andsaid layer and provided with respective means for spacing the liner fromthe respective platens and for subjecting each of said liners to arespective stream of said cooling fluid.

3. The improvement defined in claim 1 wherein said press is a multilevelpress having a plurality of vertically spaced horizontal platensdefining respective stages between respective upper and lower platens,at least the lower platen of each stage being heated and being providedwith a respective liner, respective means for spacing each of saidliners from the respective lower platen upon opening of the press, andrespective means for subjecting each of the liners to a respectivestream of cooling fluid.

4. The improvement defined in claim 3 wherein the means for spacing eachof said liners from the respective lower platen of the respective stagesis constructed and arranged to form a gap of the order of 0.8 mm.between each liner and the respective lower platen, said means forsubjecting said liners to a respective stream of cooling fluid beingformed as respective arrays of nozzles directing respective jets of airover the upper surfaces of said liners.

5. In an installation for producing pressed board wherein a layer ofcomminuted material is hot-pressed to form a coherent sheet andincluding a platen press having at least one pressing stage and at leasttwo platens receiving said layer between them, means for heating atleast one of said platens, means for relatively shifting said platenstoward and away from one another to compress said layer and releasesame, the improvement which comprises:

at least one sheet-metal liner interposed between said layer and saidone of said platens for heat-conductive surface contact therewith uponmovement of said platens toward one another for transferring heat tosaid layer;

means operatively connected with said liner and effective upon movementof said platens away from one another to space said liner from said oneof said platens and break heat-conductive contact therebetween at leastalong the major portions of thesurfaces of said liner and said one ofsaid platens; and means for subjecting said liner to a stream of acooling fluid, said means for spacing said liner from said 7 one of saidplatens comprising a respective elastic support at opposite edges ofsaid one of said platens, said liner spanning said support while beingretained thereby in spaced relationship from said one of said platens inan open condition of the press but being resiliently urged into surfacecontact with said one of said platens to stress said supports uponclosure of the press with a layer between said platens, said supportsbeing respective elastic members extending transversely of said one ofsaid platens and projecting therebeyond by a distance approximatelycorresponding to the spacing between said liner and said one of saidplatens in said open condition of the press, said members beingdeflectable inwardly toward said press stage upon press closure, saidone of said platens being provided along its opposite surfaces with apair of said liners, said members lying generally in planesperpendicular to said one of said platens and extending in therespective planes over a width exceeding that of said platens, saidmeans for spacing said liners from said one of said platens-furthercomprising bolt means slidably extending through said members forsecuring same to said one of said platens at said opposite edges, andspacer elements between said edges and the respective members, saidspacer elements having widths less than the thickness of said one ofsaid platens, said bolt means passing through the respective member andelement.

References Cited UNITED STATES PATENTS FOREIGN PATENTS /1966 Germany.

PETER FELDMAN, Primary Examiner US. Cl. X.R.

